1. Field of the Invention
The present invention relates to a pneumatic tire capable of reducing tire noise without deteriorating other performance.
2. Description of the Related Art
In order to improve mud performance of tire while reducing tire noise, JP2004-58839A1 discloses a pneumatic tire as shown in FIG. 5. The tire includes a tread portion provided with: a shoulder main groove “a” disposed the nearest side of the tread edge Te; a plurality of shoulder lateral grooves b extending from the shoulder main groove toward the tread edge Te; and a plurality of middle lateral grooves c extending from the shoulder main groove “a” toward the tire equatorial plane Co.
The shoulder lateral grooves b include a first shoulder lateral groove bL having a large groove width and a second shoulder lateral groove bS having a small groove width compared to the first shoulder lateral groove bL. The first shoulder lateral groove bL and the second shoulder lateral groove bS are alternately arranged in a tire circumferential direction.
Additionally, the first and second shoulder lateral grooves bL, bS have the following relations:WLi/WSi<WLo/WSo.
Here, WLi and WLo are groove widths of the first shoulder lateral groove bL at the axially inner and outer ends, respectively, and WSi and WSo are groove widths of the second shoulder lateral groove bS at the axially inner and outer ends, respectively.
Since the tire above has the first and second shoulder lateral grooves bL, bS arranged alternately with different groove widths, pitch noise is modulated into a wide frequency range so that the pattern noise turns to the so called white noise. Additionally, since the first shoulder lateral groove bL has a large groove width WLo at the tread edge Te, mud performance of the tire improves. Additionally, since the first shoulder lateral groove bL has the small groove width WLi at the inner end so as to decrease a groove volume thereof, tire noise reduces.
However, consumers request still further improved tire with low noise.